Traditionally, important and customer unique mailpieces, such as bank statements, credit card statements, phone bills etc., are printed on high speed laser or inkjet printers. A typical print run may contain 20,000 customer statements. After printing, the statements are collated, should there be more than one page per statement, folded and inserted at high speed into an envelope for delivery to the postal service.
Because of the speed and complexity of statement production, there is always the possibility of paper jams, operator error, such that a page may be inserted in the incorrect envelope by mistake. A high degree of quality control during production is therefore necessary to avoid such mistakes, which could have the adverse marketing effect of seriously questioning the issuing bank's security procedures.
Normally, the customer name and address is printed on the first statement page, such that, when folded, it is still visible. A window envelope is used to carry the statement, with the customer address so positioned that it is visible through this window, and can thus be delivered by the postal service.
There are two main disadvantages to this method.                1. Window envelopes are more expensive to produce than normal, closed face envelopes.        2. Marketing professionals would prefer a closed face envelope, to give the impression of a more “valuable” personalised communication, not just yet another bill.        
Use of a window envelope has the benefit of higher security, but the above two disadvantages.
A closed face envelope can be used, but it is then necessary to print the customer name and address on the outside of this envelope. If the contents are non-unique, for example a general marketing message, then a database of target customers can feed an inkjet printer with controls to print each address, and it is not material if the addresses get out of sequence due to machine or operator malfunction, because all contents are identical.
In the case of personalised contents, like bank statements, a possible solution lies in using a camera to read a printed code on the statement just before it is inserted into the envelope, and remember that code. Once the completed envelope has reached the end of the insertion machine (which could be three meters and two seconds in time later, during which other envelopes are passing through their own part of the cycle), the remembered code is fed to the closed face inkjet printer for addressing that particular customer mailpiece.
Disadvantages with this solution are:                1. The insertion machine may jam or get out of step during that critical three meters delay.        2. The operator has no way to verify that the correct contents match the outside address, unless he opens and destroys samples during production.        